Glass ribbon machines and other apparatus for making proto-bulbs for hollow glass article such as, e.g., incandescent lamps, are well known. Such machines are exemplified by those shown in U.S. Pat. Nos. 3,642,461; 3,647,410; and 3,775,084, and the teachings of these patents are herein incorporated by reference.
The orifice plate, through which the molten glass is expelled for the forming operation, is an integral part of the ribbon machines.
The standard design for orifice plates has included an orifice in the form of an inverted infundibulum which may be counterbored. The sides of the orifice, at least above any counterbore, form a constant angle of between 11.degree. and 15.degree. from the vertical.
It has now been discovered that this plate design often causes catastrophic breakage of the glass article being formed, either when it is being removed from the machine or subsequently, during handling and use.